rust-test

Rust TDD Command

This command enforces test-driven development methodology for Rust code using #[test], rstest, proptest, and mockall.

What This Command Does

1. Define Types/Traits: Scaffold function signatures with todo!()
2. Write Tests: Create comprehensive test module (RED)
3. Run Tests: Verify tests fail for the right reason
4. Implement Code: Write minimal code to pass (GREEN)
5. Refactor: Improve while keeping tests green
6. Check Coverage: Ensure 80%+ coverage with cargo-llvm-cov

When to Use

Use /rust-test when:

• Implementing new Rust functions, methods, or traits
• Adding test coverage to existing Rust code
• Fixing bugs (write failing test first)
• Building critical business logic
• Learning TDD workflow in Rust

TDD Cycle

RED     -> Write failing test first
GREEN   -> Implement minimal code to pass
REFACTOR -> Improve code, tests stay green
REPEAT  -> Next test case

Example Session

User: /rust-test I need a function to validate user registration

Agent:
# TDD Session: Registration Validator

## Step 1: Define Interface

```rust
// src/validator.rs
pub struct RegistrationRequest {
    pub name: String,
    pub email: String,
    pub password: String,
}

pub enum ValidationResult {
    Valid,
    Invalid(Vec<String>),
}

pub fn validate_registration(request: &RegistrationRequest) -> ValidationResult {
    todo!()
}
```

## Step 2: Write Tests (RED)

```rust
#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn valid_registration_returns_valid() {
        let request = RegistrationRequest {
            name: "Alice".into(),
            email: "[email protected]".into(),
            password: "SecureP@ss1".into(),
        };
        assert!(matches!(validate_registration(&request), ValidationResult::Valid));
    }

    #[test]
    fn blank_name_returns_invalid() {
        let request = RegistrationRequest {
            name: "".into(),
            email: "[email protected]".into(),
            password: "SecureP@ss1".into(),
        };
        match validate_registration(&request) {
            ValidationResult::Invalid(errors) => {
                assert!(errors.contains(&"Name is required".to_string()));
            }
            ValidationResult::Valid => panic!("expected Invalid"),
        }
    }